Are you two serious? Those two comments are ridiculous.
Yes and no: Is it realistic that we'll have another civil war? Probably not
Is it realistic that it would not happen decades from now? Probably
Now, what part of the comment is rediculous? Me talking about how social democracies don't work? Please, don't take it too seriously, were going to have disagreements, and since reforming or nationalizing the government is an ideology there's no easy way to debate it.
The part of your comment when you say that a constitutional republic is incompatible with a social democracy; what part of a social democracy as you understand it is incompatible with an American constitutional republic?
And the civil war bit is so silly I'm afraid to answer it. Unless there's a total collapse of government legitimacy and authority, there isn't going to be a civil war for a long time. A coup, maybe, but not a civil war.